/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.util.function;

import org.apache.flink.annotation.Public;

import java.util.function.Function;

/**
 * A functional interface for a {@link java.util.function.Function} that may throw exceptions.
 *
 * @param <T> The type of the argument to the function.
 * @param <R> The type of the result of the supplier.
 * @param <E> The type of Exceptions thrown by this function.
 */
@Public
@FunctionalInterface
public interface FunctionWithException<T, R, E extends Throwable> {

    /**
     * Calls this function.
     *
     * @param value The argument to the function.
     * @return The result of thus supplier.
     * @throws E This function may throw an exception.
     */
    R apply(T value) throws E;

    /**
     * Convert at {@link FunctionWithException} into a {@link Function}.
     *
     * @param functionWithException function with exception to convert into a function
     * @param <A> input type
     * @param <B> output type
     * @return {@link Function} which throws all checked exception as an unchecked exception.
     */
    static <A, B> Function<A, B> unchecked(FunctionWithException<A, B, ?> functionWithException) {
        return (A a) -> {
            try {
                return functionWithException.apply(a);
            } catch (Throwable t) {
                ThrowingExceptionUtils.rethrow(t);
                // we need this to appease the compiler :-(
                return null;
            }
        };
    }
}
